The “freeze_support()“ line can be omitted if the program xxx

python3运行 concurrent.futures 报错

RuntimeError: 
        An attempt has been made to start a new process before the
        current process has finished its bootstrapping phase.

        This probably means that you are not using fork to start your
        child processes and you have forgotten to use the proper idiom
        in the main module:

            if __name__ == '__main__':
                freeze_support()
                ...

        The "freeze_support()" line can be omitted if the program
        is not going to be frozen to produce an executable.

报错很清楚看到提示： 多进程调用必须放到 代码块 if __name__ == '__main__': 下面，即 main函数 程序入口处